The Race to Find Life

Feb. 28, 2002

by Seth Shostak - Senior Astronomer

The Olympics may still be fresh in your mind, but there's another competition underway whose consequences will hang over the planet a lot longer than this year's pairs skating. It's the race to find the first unequivocal evidence of life somewhere other than Earth.

There are two things that are particularly intriguing about this effort: (1) The contestants are running towards wildly different finish lines, and (2) despite the variety of approaches, it's impossible to "call" the race. Anyone could win.

Now of course, there are some folks (quite a few, actually) who figure that this race is over, and reluctant scientists are just being difficult about handing over the loving cup. For example, there's the claim that fossilized microbes have been found in martian meteorites, not to mention the widespread belief that intelligent aliens are visiting Earth. Most scientists are skeptical of both, not because they're fuddy-duddies incapable of thinking out of the box, but because the evidence presented so far has failed to sway their naturally (and correctly) skeptical natures.

So who are the other contestants in the competition to be the first to find cosmic biology?

To begin with, there's an impressive effort being made to turn up simple life in our solar system by sending spacecraft to likely habitats -- Mars and Jupiter's moon, Europa. The Red Planet, as everyone and their dog knows, is the nearby world most like Earth. Although its surface is aggressively hostile, there could be liquid water underneath, possibly filled with living organisms. The Odyssey spacecraft is now gearing up to survey for evidence of underground water, and landers and additional orbiters will be sent Mars-ward over the next decade. But convincing proof of Martians -- either dead or alive -- may have to await a sample return mission. That will happen in 2014 or maybe 2016.

The next reconnaissance of Europa will be the Europa Orbiter, a craft that will glide around this ice-covered moon using an altimeter and radar to decide whether it has a massive, subsurface ocean and, if it does, to look for thin spots in the crust. Assuming that the Orbiter does both, then follow-up missions would actually land on Europa and hunt for evidence of organic materials on the surface that may have leaked through the ice, or (eventually) drill down several kilometers to the ocean below. Orbiter is now planned for 2010, but the landers -- which could find Europan biology -- won't be sent until later.

Then there are plans to find and image Earth-size planets, including analyzing the light reflected off their atmospheres in the hope of finding oxygen, water vapor, or methane. The right combination of these ingredients would be a strong tip-off that biology is grinding away on these worlds. The Terrestrial Planet Finder and Europe's Darwin project -- both of which could find simple life at a distance -- are scheduled for launch as early as 2011.

Finally, there are the SETI experiments to eavesdrop on technological life. We talk about that a lot in these columns. I will only add here that, if all goes well, the Allen Telescope Array will be good to go by 2005, and will have checked out a million star systems by the year 2020.

What's the bottom line? Various researchers are looking for life, both simple and sophisticated, both nearby and at great distance. Any of their attempts might succeed, and the time frame of their efforts suggests someone will cross the finish line in the next two decades.

Of course, the first sure evidence for life elsewhere will only be found once in all human history. I figure someone strutting the planet right now is going to be the winner in a race that will be remembered forever.